class Compiler {
    constructor(vm) {
        this.el = vm.$el;
        this.vm = vm;
        this.methods = vm.$methods;
        this.compile(this.el);
    }
    //编译模板，处理文本节点和元素节点
    compile(el) {
        let childNodes = el.childNodes
        Array.from(childNodes).forEach(node => {
            //处理文本节点
            if (this.isTextNode(node)) {
                this.compileText(node)
            } else if (this.isElementNode(node)) {
                //处理元素节点
                this.compileElement(node)
            }
            //判断node节点是否有子节点，如果有子节点，要递归调用compile
            if(node.childNodes && node.childNodes.length) {
                this.compile(node)
            }
        })
    }

    //编译元素节点，处理指令
    compileElement(node) {
        //遍历所有的属性节点
        Array.from(node.attributes).forEach(attr => {
            //判断是否是指令
            let attrName = attr.name
            if (this.isDirective(attrName)) {
                attrName = attrName.substr(2)
                if (attrName.startsWith('on')) {
                    attrName = 'click'
                }
                let key = attr.value
                this.update(node, key, attrName)
            }
        })
    }
    update(node, key, attrName) {
        let updateFn = this[attrName+'Updater']
        if (attrName==='click') {
            updateFn && updateFn.call(this, node, this.methods[key], key)
        } else {
            updateFn && updateFn.call(this, node, this.vm[key], key)
        }
    }
    textUpdater(node, value, key) {
        node.textContent = value
        new Watcher(this.vm, key, (newValue)=>{
            node.textContent = newValue
        })
    }
    modelUpdater(node, value, key) {
        node.value = value
        new Watcher(this.vm, key, (newValue)=>{
            node.value = newValue
        })
        // 双向绑定
        node.addEventListener('input', ()=>{
            this.vm[key] = node.value
        })
    }
    htmlUpdater(node, value, key) {
        node.innerHTML  = value
        new Watcher(this.vm, key, (newValue)=>{
            node.innerHTML  = newValue
        })
    }
    clickUpdater(node, fn, key) {
        console.log(node, fn, key)
        node.addEventListener('click', () => {
            this.methods[key].call(this.vm)
        })
    }

    //编译本文节点，处理差值表达式
    compileText(node) {
        let reg = /\{\{(.+?)\}\}/
        let value = node.textContent
        if (reg.test(value)) {
            let key = RegExp.$1.trim()
            node.textContent = value.replace(reg, this.vm[key])

            // 创建watcher对象，当数据改变更新视图
            new Watcher(this.vm, key, (newValue) => {
                node.textContent = newValue
            })
        }
    }

    //判断元素属性是否为指令
    isDirective(attrName) {
        return attrName.startsWith('v-')
    }

    //判断节点是否是文本节点
    isTextNode(node) {
        return node.nodeType === 3
    }

    //判断节点是否是元素节点
    isElementNode(node) {
        return node.nodeType === 1
    }
}